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Gotora PT, van der Sluis R, Williams ME. HIV-1 Tat amino acid residues that influence Tat-TAR binding affinity: a scoping review. BMC Infect Dis 2023; 23:164. [PMID: 36932337 PMCID: PMC10020771 DOI: 10.1186/s12879-023-08123-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 02/27/2023] [Indexed: 03/19/2023] Open
Abstract
HIV-1 remains a global health concern and to date, nearly 38 million people are living with HIV. The complexity of HIV-1 pathogenesis and its subsequent prevalence is influenced by several factors including the HIV-1 subtype. HIV-1 subtype variation extends to sequence variation in the amino acids of the HIV-1 viral proteins. Of particular interest is the transactivation of transcription (Tat) protein due to its key function in viral transcription. The Tat protein predominantly functions by binding to the transactivation response (TAR) RNA element to activate HIV-1 transcriptional elongation. Subtype-specific Tat protein sequence variation influences Tat-TAR binding affinity. Despite several studies investigating Tat-TAR binding, it is not clear which regions of the Tat protein and/or individual Tat amino acid residues may contribute to TAR binding affinity. We, therefore, conducted a scoping review on studies investigating Tat-TAR binding. We aimed to synthesize the published data to determine (1) the regions of the Tat protein that may be involved in TAR binding, (2) key Tat amino acids involved in TAR binding and (3) if Tat subtype-specific variation influences TAR binding. A total of thirteen studies met our inclusion criteria and the key findings were that (1) both N-terminal and C-terminal amino acids outside the basic domain (47-59) may be important in increasing Tat-TAR binding affinity, (2) substitution of the amino acids Lysine and Arginine (47-59) resulted in a reduction in binding affinity to TAR, and (3) none of the included studies have investigated Tat subtype-specific substitutions and therefore no commentary could be made regarding which subtype may have a higher Tat-TAR binding affinity. Future studies investigating Tat-TAR binding should therefore use full-length Tat proteins and compare subtype-specific variations. Studies of such a nature may help explain why we see differential pathogenesis and prevalence when comparing HIV-1 subtypes.
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2
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Huang K, Fang X. A review on recent advances in methods for site-directed spin labeling of long RNAs. Int J Biol Macromol 2023; 239:124244. [PMID: 37001783 DOI: 10.1016/j.ijbiomac.2023.124244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 01/12/2023] [Accepted: 03/15/2023] [Indexed: 03/31/2023]
Abstract
RNAs are important biomolecules that play essential roles in various cellular processes and are crucially linked with many human diseases. The key to elucidate the mechanisms underlying their biological functions and develop RNA-based therapeutics is to investigate RNA structure and dynamics and their connections to function in detail using a variety of approaches. Magnetic resonance techniques including paramagnetic nuclear magnetic resonance (NMR) and electron magnetic resonance (EPR) spectroscopies have proved to be powerful tools to gain insights into such properties. The prerequisites for paramagnetic NMR and EPR studies on RNAs are to achieve site-specific spin labeling of the intrinsically diamagnetic RNAs, which however is not trivial, especially for long ones. In this review, we present some covalent labeling strategies that allow site-specific introduction of electron spins to long RNAs. Generally, these strategies include assembly of long RNAs via enzymatic ligation of short oligonucleotides, co- and post-transcriptional site-specific labeling empowered with the unnatural base pair system, and direct enzymatic functionalization of natural RNAs. We introduce a few case studies to discuss the advantages and limitations of each strategy, and to provide a vision for the future development.
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3
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Miao Q, Nitsche C, Orton H, Overhand M, Otting G, Ubbink M. Paramagnetic Chemical Probes for Studying Biological Macromolecules. Chem Rev 2022; 122:9571-9642. [PMID: 35084831 PMCID: PMC9136935 DOI: 10.1021/acs.chemrev.1c00708] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Indexed: 12/11/2022]
Abstract
Paramagnetic chemical probes have been used in electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopy for more than four decades. Recent years witnessed a great increase in the variety of probes for the study of biological macromolecules (proteins, nucleic acids, and oligosaccharides). This Review aims to provide a comprehensive overview of the existing paramagnetic chemical probes, including chemical synthetic approaches, functional properties, and selected applications. Recent developments have seen, in particular, a rapid expansion of the range of lanthanoid probes with anisotropic magnetic susceptibilities for the generation of structural restraints based on residual dipolar couplings and pseudocontact shifts in solution and solid state NMR spectroscopy, mostly for protein studies. Also many new isotropic paramagnetic probes, suitable for NMR measurements of paramagnetic relaxation enhancements, as well as EPR spectroscopic studies (in particular double resonance techniques) have been developed and employed to investigate biological macromolecules. Notwithstanding the large number of reported probes, only few have found broad application and further development of probes for dedicated applications is foreseen.
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Affiliation(s)
- Qing Miao
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333 CC, The Netherlands
- School
of Chemistry &Chemical Engineering, Shaanxi University of Science & Technology, Xi’an710021, China
| | - Christoph Nitsche
- Research
School of Chemistry, The Australian National
University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
| | - Henry Orton
- Research
School of Chemistry, The Australian National
University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
- ARC
Centre of Excellence for Innovations in Peptide & Protein Science,
Research School of Chemistry, Australian
National University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
| | - Mark Overhand
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333 CC, The Netherlands
| | - Gottfried Otting
- Research
School of Chemistry, The Australian National
University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
- ARC
Centre of Excellence for Innovations in Peptide & Protein Science,
Research School of Chemistry, Australian
National University, Sullivans Creek Road, Canberra, Australian Capital Territory 2601, Australia
| | - Marcellus Ubbink
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, Leiden 2333 CC, The Netherlands
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4
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Wang H, Huang N, Dangerfield T, Johnson KA, Gao J, Elber R. Exploring the Reaction Mechanism of HIV Reverse Transcriptase with a Nucleotide Substrate. J Phys Chem B 2020; 124:4270-4283. [PMID: 32364738 PMCID: PMC7260111 DOI: 10.1021/acs.jpcb.0c02632] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Enzymatic reactions consist of several steps: (i) a weak binding event of the substrate to the enzyme, (ii) an induced fit or a protein conformational transition upon ligand binding, (iii) the chemical reaction, and (iv) the release of the product. Here we focus on step iii of the reaction of a DNA polymerase, HIV RT, with a nucleotide. We determine the rate and the free energy profile for the addition of a nucleotide to a DNA strand using a combination of a QM/MM model, the string method, and exact Milestoning. The barrier height and the time scale of the reaction are consistent with experiment. We show that the observables (free energies and mean first passage time) converge rapidly, as a function of the Milestoning iteration number. We also consider the substitution of an oxygen of the incoming nucleotide by a nonbridging sulfur atom and its impact on the enzymatic reaction. This substitution has been suggested in the past as a tool to examine the influence of the chemical step on the overall rate. Our joint computational and experimental study suggests that the impact of the substitution is small. Computationally, the differences between the two are within the estimated error bars. Experiments suggest a small difference. Finally, we examine step i, the weak binding of the nucleotide to the protein surface. We suggest that this step has only a small contribution to the selectivity of the enzyme. Comments are made on the impact of these steps on the overall mechanism.
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Affiliation(s)
- Hao Wang
- Oden Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin TX 78712
| | - Nathan Huang
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712
| | - Tyler Dangerfield
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712
| | - Kenneth A. Johnson
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712
| | - Jiali Gao
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455-0431
| | - Ron Elber
- Oden Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin TX 78712
- Department of Chemistry, University of Texas at Austin, Austin, TX 78712
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5
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Arjmand F, Afsan Z, Sharma S, Parveen S, Yousuf I, Sartaj S, Siddique HR, Tabassum S. Recent advances in metallodrug-like molecules targeting non-coding RNAs in cancer chemotherapy. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2019.02.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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6
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Arjmand F, Afsan Z, Roisnel T. Design, synthesis and characterization of novel chromone based-copper(ii) antitumor agents with N,N-donor ligands: comparative DNA/RNA binding profile and cytotoxicity. RSC Adv 2018; 8:37375-37390. [PMID: 35557803 PMCID: PMC9089433 DOI: 10.1039/c8ra06722h] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 10/23/2018] [Indexed: 01/05/2023] Open
Abstract
A series of new chromone based-Cu(ii) complexes 1–3 derived from bioactive pharmacophore, 3-formylchromone and N,N-donor ligands viz., 1,10-phenanthroline, 2,2′-bipyridine and 1R,2R-DACH were synthesized as potential antitumor agents and thoroughly characterized by UV-vis, FT-IR, EPR, ESI-MS and elemental analysis. Single X-crystal diffraction studies of complex 2 revealed triclinic P1̄ space group with square pyramidal geometry around the Cu(ii) center. Comparative in vitro binding studies with ct-DNA and tRNA were carried out using absorption and emission titration experiments which revealed intercalative mode of binding with higher binding propensity of complexes 1–3 towards tRNA as compared to ct-DNA. Additionally, complex 1 exhibited high binding affinity among all the three complexes due to the involvement of phen co-ligands via π-stacking interactions in between nucleic acid base pairs. Furthermore, Hirshfeld surface analysis was carried out for complex 2 to investigate various intra and intermolecular non-covalent interactions (H-bonding, C–H⋯π etc.) accountable for stabilization of crystal lattice. The cleavage activity of complex 1 was performed by gel electrophoretic assay with pBR322 DNA and tRNA which revealed efficient DNA/tRNA cleaving ability of complex, suggesting tRNA cleavage both concentration and time dependent. Furthermore, in vitro cytotoxic activity of complexes 1–3 on a selected panel of human cancer cell lines was performed which revealed that all three complexes exhibited remarkably good cytotoxic activity with GI50 value < 10 μg mL−1 (<20 μM). New chromone-based Cu(ii) tRNA targeted complexes 1–3 as potential anticancer agents have been synthesized and thoroughly characterized.![]()
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Affiliation(s)
- Farukh Arjmand
- Department of Chemistry
- Aligarh Muslim University
- Aligarh 202002
- India
| | - Zeenat Afsan
- Department of Chemistry
- Aligarh Muslim University
- Aligarh 202002
- India
| | - Thierry Roisnel
- Institut des Sciences Chimiques de Rennes
- UMR 6226, Université de Rennes 1
- 15335042 Rennes
- France
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7
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Merriman DK, Xue Y, Yang S, Kimsey IJ, Shakya A, Clay M, Al-Hashimi HM. Shortening the HIV-1 TAR RNA Bulge by a Single Nucleotide Preserves Motional Modes over a Broad Range of Time Scales. Biochemistry 2016; 55:4445-56. [PMID: 27232530 DOI: 10.1021/acs.biochem.6b00285] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Helix-junction-helix (HJH) motifs are flexible building blocks of RNA architecture that help define the orientation and dynamics of helical domains. They are also frequently involved in adaptive recognition of proteins and small molecules and in the formation of tertiary contacts. Here, we use a battery of nuclear magnetic resonance techniques to examine how deleting a single bulge residue (C24) from the human immunodeficiency virus type 1 (HIV-1) transactivation response element (TAR) trinucleotide bulge (U23-C24-U25) affects dynamics over a broad range of time scales. Shortening the bulge has an effect on picosecond-to-nanosecond interhelical and local bulge dynamics similar to that casued by increasing the Mg(2+) and Na(+) concentration, whereby a preexisting two-state equilibrium in TAR is shifted away from a bent flexible conformation toward a coaxial conformation, in which all three bulge residues are flipped out and flexible. Surprisingly, the point deletion minimally affects microsecond-to-millisecond conformational exchange directed toward two low-populated and short-lived excited conformational states that form through reshuffling of bases pairs throughout TAR. The mutant does, however, adopt a slightly different excited conformational state on the millisecond time scale, in which U23 is intrahelical, mimicking the expected conformation of residue C24 in the excited conformational state of wild-type TAR. Thus, minor changes in HJH topology preserve motional modes in RNA occurring over the picosecond-to-millisecond time scales but alter the relative populations of the sampled states or cause subtle changes in their conformational features.
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Affiliation(s)
- Dawn K Merriman
- Department of Chemistry, Duke University , Durham, North Carolina 27708, United States
| | - Yi Xue
- Department of Biochemistry, Duke University Medical Center , Durham, North Carolina 27710, United States
| | - Shan Yang
- Baxter Health Care (Suzhou) Company, Ltd. , Suzhou, Jiang Su 215028, China
| | - Isaac J Kimsey
- Department of Biochemistry, Duke University Medical Center , Durham, North Carolina 27710, United States
| | - Anisha Shakya
- Department of Chemistry and Biophysics, University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Mary Clay
- Department of Biochemistry, Duke University Medical Center , Durham, North Carolina 27710, United States
| | - Hashim M Al-Hashimi
- Department of Chemistry, Duke University , Durham, North Carolina 27708, United States.,Department of Biochemistry, Duke University Medical Center , Durham, North Carolina 27710, United States
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8
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Meyer A, Abdullin D, Schnakenburg G, Schiemann O. Single and double nitroxide labeled bis(terpyridine)-copper(ii): influence of orientation selectivity and multispin effects on PELDOR and RIDME. Phys Chem Chem Phys 2016; 18:9262-71. [DOI: 10.1039/c5cp07621h] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The structure of Jahn–Teller distorted copper–nitroxide complexes in neutral and acidic solutions is investigated using EPR distance measurements taking into account the influence of orientation selectivity and multispin effects.
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Affiliation(s)
- Andreas Meyer
- Institute of Physical and Theoretical Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53115 Bonn
- Germany
| | - Dinar Abdullin
- Institute of Physical and Theoretical Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53115 Bonn
- Germany
| | - Gregor Schnakenburg
- Institute of Inorganic Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53121 Bonn
- Germany
| | - Olav Schiemann
- Institute of Physical and Theoretical Chemistry
- Rheinische Friedrich-Wilhelms-University Bonn
- 53115 Bonn
- Germany
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9
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10
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Saha S, Jagtap AP, Sigurdsson ST. Site-Directed Spin Labeling of RNA by Postsynthetic Modification of 2'-Amino Groups. Methods Enzymol 2015; 563:397-414. [PMID: 26478493 DOI: 10.1016/bs.mie.2015.07.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
To elucidate mechanisms that govern functions of nucleic acids, it is essential to understand their structure and dynamics. Electron paramagnetic resonance (EPR) spectroscopy is a valuable technique that is routinely used to study those aspects of nucleic acids. A prerequisite for most EPR studies of nucleic acids is incorporation of spin labels at specific sites, known as site-directed spin labeling (SDSL). There are two main strategies for SDSL through formation of covalent bonds, i.e., the phosphoramidite approach and postsynthetic spin-labeling. After describing briefly the advantages and disadvantages of these two strategies, postsynthetic labeling of 2'-amino groups in RNA is delineated. Postsynthetic labeling of 2'-amino groups in RNA using 4-isocyanato-TEMPO has long been established as a useful approach. However, this method has some drawbacks, both with regard to the spin-labeling protocol and the flexibility of the spin label itself. Recently reported isothiocyanate-substituted aromatic isoindoline-derived nitroxides can be used to quantitatively and selectively modify 2'-amino groups in RNA and do not have the drawbacks associated with 4-isocyanato-TEMPO. This chapter provides a detailed description of the postsynthetic spin-labeling methods of 2'-amino groups in RNA with a special focus on using the aromatic isothiocyanate spin labels.
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Affiliation(s)
- Subham Saha
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Anil P Jagtap
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland.
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11
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Ding Y, Zhang X, Tham KW, Qin PZ. Experimental mapping of DNA duplex shape enabled by global lineshape analyses of a nucleotide-independent nitroxide probe. Nucleic Acids Res 2014; 42:e140. [PMID: 25092920 PMCID: PMC4191381 DOI: 10.1093/nar/gku695] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Sequence-dependent variation in structure and dynamics of a DNA duplex, collectively referred to as ‘DNA shape’, critically impacts interactions between DNA and proteins. Here, a method based on the technique of site-directed spin labeling was developed to experimentally map shapes of two DNA duplexes that contain response elements of the p53 tumor suppressor. An R5a nitroxide spin label, which was covalently attached at a specific phosphate group, was scanned consecutively through the DNA duplex. X-band continuous-wave electron paramagnetic resonance spectroscopy was used to monitor rotational motions of R5a, which report on DNA structure and dynamics at the labeling site. An approach based on Pearson's coefficient analysis was developed to collectively examine the degree of similarity among the ensemble of R5a spectra. The resulting Pearson's coefficients were used to generate maps representing variation of R5a mobility along the DNA duplex. The R5a mobility maps were found to correlate with maps of certain DNA helical parameters, and were capable of revealing similarity and deviation in the shape of the two closely related DNA duplexes. Collectively, the R5a probe and the Pearson's coefficient-based lineshape analysis scheme yielded a generalizable method for examining sequence-dependent DNA shapes.
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Affiliation(s)
- Yuan Ding
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
| | - Xiaojun Zhang
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
| | - Kenneth W Tham
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
| | - Peter Z Qin
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
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12
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Göbl C, Madl T, Simon B, Sattler M. NMR approaches for structural analysis of multidomain proteins and complexes in solution. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2014; 80:26-63. [PMID: 24924266 DOI: 10.1016/j.pnmrs.2014.05.003] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 05/14/2014] [Indexed: 05/22/2023]
Abstract
NMR spectroscopy is a key method for studying the structure and dynamics of (large) multidomain proteins and complexes in solution. It plays a unique role in integrated structural biology approaches as especially information about conformational dynamics can be readily obtained at residue resolution. Here, we review NMR techniques for such studies focusing on state-of-the-art tools and practical aspects. An efficient approach for determining the quaternary structure of multidomain complexes starts from the structures of individual domains or subunits. The arrangement of the domains/subunits within the complex is then defined based on NMR measurements that provide information about the domain interfaces combined with (long-range) distance and orientational restraints. Aspects discussed include sample preparation, specific isotope labeling and spin labeling; determination of binding interfaces and domain/subunit arrangements from chemical shift perturbations (CSP), nuclear Overhauser effects (NOEs), isotope editing/filtering, cross-saturation, and differential line broadening; and based on paramagnetic relaxation enhancements (PRE) using covalent and soluble spin labels. Finally, the utility of complementary methods such as small-angle X-ray or neutron scattering (SAXS, SANS), electron paramagnetic resonance (EPR) or fluorescence spectroscopy techniques is discussed. The applications of NMR techniques are illustrated with studies of challenging (high molecular weight) protein complexes.
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Affiliation(s)
- Christoph Göbl
- Biomolecular NMR and Center for Integrated Protein Science Munich at Department Chemie, Technische Universität München, Garching, Germany
| | - Tobias Madl
- Biomolecular NMR and Center for Integrated Protein Science Munich at Department Chemie, Technische Universität München, Garching, Germany; Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg, Germany; Institute of Molecular Biology, University of Graz, Graz, Austria.
| | - Bernd Simon
- European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Michael Sattler
- Biomolecular NMR and Center for Integrated Protein Science Munich at Department Chemie, Technische Universität München, Garching, Germany; Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg, Germany.
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13
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Sun Y, Zhang Z, Grigoryants VM, Myers WK, Liu F, Earle KA, Freed JH, Scholes CP. The internal dynamics of mini c TAR DNA probed by electron paramagnetic resonance of nitroxide spin-labels at the lower stem, the loop, and the bulge. Biochemistry 2012; 51:8530-41. [PMID: 23009298 DOI: 10.1021/bi301058q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Electron paramagnetic resonance (EPR) at 236.6 and 9.5 GHz probed the tumbling of nitroxide spin probes in the lower stem, in the upper loop, and near the bulge of mini c TAR DNA. High-frequency 236.6 GHz EPR, not previously applied to spin-labeled oligonucleotides, was notably sensitive to fast, anisotropic, hindered local rotational motion of the spin probe, occurring approximately about the NO nitroxide axis. Labels attached to the 2'-aminocytidine sugar in the mini c TAR DNA showed such anisotropic motion, which was faster in the lower stem, a region previously thought to be partially melted. More flexible labels attached to phosphorothioates at the end of the lower stem tumbled isotropically in mini c TAR DNA, mini TAR RNA, and ψ(3) RNA, but at 5 °C, the motion became more anisotropic for the labeled RNAs, implying more order within the RNA lower stems. As observed by 9.5 GHz EPR, the slowing of nanosecond motions of large segments of the oligonucleotide was enhanced by increasing the ratio of the nucleocapsid protein NCp7 to mini c TAR DNA from 0 to 2. The slowing was most significant at labels in the loop and near the bulge. At a 4:1 ratio of NCp7 to mini c TAR DNA, all labels reported tumbling times of >5 ns, indicating a condensation of NCp7 and TAR DNA. At the 4:1 ratio, pulse dipolar EPR spectroscopy of bilabels attached near the 3' and 5' termini showed evidence of an NCp7-induced increase in the 3'-5' end-to-end distance distribution and a partially melted stem.
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Affiliation(s)
- Yan Sun
- Department of Chemistry, University at Albany, 1400 Washington Avenue, Albany, NY 12222, USA
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14
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Cekan P, Sigurdsson ST. Conformation and dynamics of nucleotides in bulges and symmetric internal loops in duplex DNA studied by EPR and fluorescence spectroscopies. Biochem Biophys Res Commun 2012; 420:656-61. [PMID: 22450317 DOI: 10.1016/j.bbrc.2012.03.059] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 03/12/2012] [Indexed: 01/02/2023]
Abstract
The dynamics and conformation of base bulges and internal loops in duplex DNA were studied using the bifunctional spectroscopic probe Ç, which becomes fluorescent (Ç(f)) upon reduction of the nitroxide functional group, along with EPR and fluorescence spectroscopies. A one-base bulge was in a conformational equilibrium between looped-out and stacked states, the former favored at higher temperature and the latter at lower temperature. Stacking of bulge bases was favored in two- and three-base bulges, independent of temperature, resulting in DNA bending as evidenced by increased fluorescence of Ç(f). EPR spectra of Ç-labeled three-, four- and five-base symmetrical interior DNA bulges at 20 °C showed low mobility, indicating that the spin-label was stacked within the loop. The spin-label mobility at 37 °C increased as the loops became larger. A considerable variation in fluorescence between different loops was observed, as well as a temperature-dependence within constructs. Fluorescence unexpectedly increased as the size of the loop decreased at 2 °C. Fluorescence of the smallest loops, where a single T·T mismatch was located between the stem region and the probe, was even larger than for the single strand, indicating a considerable local structural deformation of these loops from regular B-DNA. These results show the value of combining EPR and fluorescence spectroscopy to study non-helical regions of nucleic acids.
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Affiliation(s)
- Pavol Cekan
- University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
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15
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16
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Structural Information from Oligonucleotides. STRUCTURAL INFORMATION FROM SPIN-LABELS AND INTRINSIC PARAMAGNETIC CENTRES IN THE BIOSCIENCES 2012. [DOI: 10.1007/430_2012_76] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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17
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Atsumi H, Maekawa K, Nakazawa S, Shiomi D, Sato K, Kitagawa M, Takui T, Nakatani K. Tandem Arrays of TEMPO and Nitronyl Nitroxide Radicals with Designed Arrangements on DNA. Chemistry 2011; 18:178-83. [DOI: 10.1002/chem.201102693] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Indexed: 12/24/2022]
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18
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Freeman ADJ, Ward R, El Mkami H, Lilley DMJ, Norman DG. Analysis of conformational changes in the DNA junction-resolving enzyme T7 endonuclease I on binding a four-way junction using EPR. Biochemistry 2011; 50:9963-72. [PMID: 22008089 DOI: 10.1021/bi2011898] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The four-way (Holliday) DNA junction is the central intermediate in homologous recombination. It is ultimately resolved into two nicked-duplex species by the action of a junction-resolving enzyme. These enzymes are highly selective for the structure of branched DNA, yet as a class these proteins impose significant distortion on their target junctions. Bacteriophage T7 endonuclease I selectively binds and cleaves DNA four-way junctions. The protein is an extremely stable dimer, comprising two globular domains joined by a β-strand bridge with each active site including amino acids from both polypeptides. The crystal structure of endonuclease I has been solved both as free protein and in complex with a DNA junction, showing that the protein, as well as the junction, becomes distorted on binding. We have therefore used site-specific spin-labeling in conjunction with EPR distance measurements to analyze induced fit in the binding of endonuclease I to a DNA four-way junction. The results support the change in protein structure as it binds to the junction. In addition, we have examined the structure of wild type and catalytically inactive mutants alone and in complex with DNA. We demonstrate the presence of hitherto undefined metastable conformational states within endonuclease I, showing how these states can be influenced by DNA-junction binding or mutations within the active sites. In addition, we demonstrate a previously unobserved instability in the N-terminal α1-helix upon active site mutation. These studies reveal that structural changes in both DNA and protein occur in the action of this junction-resolving enzyme.
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Affiliation(s)
- Alasdair D J Freeman
- Nucleic Acid Structure Research Group, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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Nguyen P, Qin PZ. RNA dynamics: perspectives from spin labels. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 3:62-72. [PMID: 21882345 DOI: 10.1002/wrna.104] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Dynamics are important and indispensible physical attributes that play essential roles in RNA function. RNA dynamics are complex, spanning vast timescales, and encompassing a large number of physical modes. The technique of site-directed spin labeling (SDSL), which derives information on local structural and dynamic features of a macromolecule by monitoring a chemically stable nitroxide radical using electron paramagnetic resonance spectroscopy, has been applied to monitor intrinsic dynamics at defined structural states as well as to probe conformational transition dynamics of RNAs. The current state of SDSL studies of RNA dynamics is summarized here. Further development and application of SDSL promise to open up many more opportunities for probing RNA dynamics and connecting dynamics to structure and function.
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Affiliation(s)
- Phuong Nguyen
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
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20
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Lu J, Kadakkuzha BM, Zhao L, Fan M, Qi X, Xia T. Dynamic ensemble view of the conformational landscape of HIV-1 TAR RNA and allosteric recognition. Biochemistry 2011; 50:5042-57. [PMID: 21553929 DOI: 10.1021/bi200495d] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
RNA conformational dynamics and the resulting structural heterogeneity play an important role in RNA functions, e.g., recognition. Recognition of HIV-1 TAR RNA has been proposed to occur via a conformational capture mechanism. Here, using ultrafast time-resolved fluorescence spectroscopy, we have probed the complexity of the conformational landscape of HIV-1 TAR RNA and monitored the position-dependent changes in the landscape upon binding of a Tat protein-derived peptide and neomycin B. In the ligand-free state, the TAR RNA samples multiple families of conformations with various degrees of base stacking around the three-nucleotide bulge region. Some subpopulations partially resemble those ligand-bound states, but the coaxially stacked state is below the detection limit. When Tat or neomycin B binds, the bulge region as an ensemble undergoes a conformational transition in a position-dependent manner. Tat and neomycin B induce mutually exclusive changes in the TAR RNA underlying the mechanism of allosteric inhibition at an ensemble level with residue-specific details. Time-resolved anisotropy decay measurements revealed picosecond motions of bases in both ligand-free and ligand-bound states. Mutation of a base pair at the bulge--stem junction has differential effects on the conformational distributions of the bulge bases. A dynamic model of the ensemble view of the conformational landscape for HIV-1 TAR RNA is proposed, and the implication of the general mechanism of RNA recognition and its impact on RNA-based therapeutics are discussed.
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Affiliation(s)
- Jia Lu
- Department of Molecular and Cell Biology, The University of Texas at Dallas, Richardson, Texas 75080, United States
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21
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Krstić I, Hänsel R, Romainczyk O, Engels JW, Dötsch V, Prisner TF. Long-Range Distance Measurements on Nucleic Acids in Cells by Pulsed EPR Spectroscopy. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201100886] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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22
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Krstić I, Hänsel R, Romainczyk O, Engels JW, Dötsch V, Prisner TF. Long-range distance measurements on nucleic acids in cells by pulsed EPR spectroscopy. Angew Chem Int Ed Engl 2011; 50:5070-4. [PMID: 21506223 DOI: 10.1002/anie.201100886] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Indexed: 12/18/2022]
Affiliation(s)
- Ivan Krstić
- Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Germany
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23
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Krstić I, Endeward B, Margraf D, Marko A, Prisner TF. Structure and dynamics of nucleic acids. Top Curr Chem (Cham) 2011; 321:159-98. [PMID: 22160388 DOI: 10.1007/128_2011_300] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this chapter we describe the application of CW and pulsed EPR methods for the investigation of structural and dynamical properties of RNA and DNA molecules and their interaction with small molecules and proteins. Special emphasis will be given to recent applications of dipolar spectroscopy on nucleic acids.
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Affiliation(s)
- Ivan Krstić
- Goethe University Frankfurt, Frankfurt am Main, Germany
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24
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Jakobsen U, Shelke SA, Vogel S, Sigurdsson ST. Site-directed spin-labeling of nucleic acids by click chemistry: detection of abasic sites in duplex DNA by EPR spectroscopy. J Am Chem Soc 2010; 132:10424-8. [PMID: 20617829 DOI: 10.1021/ja102797k] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This paper describes a spin label that can detect and identify local structural deformations in duplex DNA, in particular abasic sites. The spin label was incorporated into DNA by a new postsynthetic approach using click-chemistry on a solid support, which simplified both the synthesis and purification of the spin-labeled oligonucleotides. A nitroxide-functionalized azide, prepared by a short synthetic route, was reacted with an oligomer containing 5-ethynyl-2'-dU. The conjugation proceeded in quantitative yield and resulted in a fairly rigid linker between the modified nucleotide and the nitroxide spin label. The spin label was used to detect, for the first time, abasic sites in duplex DNA by X-band CW-EPR spectroscopy and give information about other structural deformations as well as local conformational changes in DNA. For example, reduced mobility of the spin label in a mismatched pair with T was consistent with the spin label displacing the T from the duplex. Addition of mercury(II) to this mispair resulted in a substantial increase in the motion of the spin label, consistent with formation of a metallopair between the T and the spin-labeled base that results in movement of the spin label out of the duplex and toward the solution. Thus, reposition of the spin label, when acting as a mercury(II)-controlled mechanical lever, can be readily detected by EPR spectroscopy. The ease of incorporation and properties of the new spin label make it attractive for EPR studies of nucleic acids and other macromolecules.
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Affiliation(s)
- Ulla Jakobsen
- Department of Physics and Chemistry, University of Southern Denmark, Nucleic Acid Center Campusvej 55, 5230 Odense, Denmark
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25
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Cekan P, Sigurdsson ST. Identification of Single-Base Mismatches in Duplex DNA by EPR Spectroscopy. J Am Chem Soc 2009; 131:18054-6. [DOI: 10.1021/ja905623k] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Pavol Cekan
- University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
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26
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Abstract
The 2'-hydroxyl group plays an integral role in RNA structure and catalysis. This ubiquitous component of the RNA backbone can participate in multiple interactions essential for RNA function, such as hydrogen bonding and metal ion coordination, but the multifunctional nature of the 2'-hydroxyl renders identification of these interactions a significant challenge. By virtue of their versatile physicochemical properties, such as distinct metal coordination preferences, hydrogen bonding properties, and ability to be protonated, 2'-amino-2'-deoxyribonucleotides can serve as tools for probing local interactions involving 2'-hydroxyl groups within RNA. The 2'-amino group can also serve as a chemoselective site for covalent modification, permitting the introduction of probes for investigation of RNA structure and dynamics. In this chapter, we describe the use of 2'-aminonucleotides for investigation of local interactions within RNA, focusing on interactions involving 2'-hydroxyl groups required for RNA structure, function, and catalysis.
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27
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Zhang X, Cekan P, Sigurdsson ST, Qin PZ. Studying RNA using site-directed spin-labeling and continuous-wave electron paramagnetic resonance spectroscopy. Methods Enzymol 2009; 469:303-28. [PMID: 20946796 DOI: 10.1016/s0076-6879(09)69015-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
In site-directed spin-labeling (SDSL), a stable nitroxide radical is attached to a specific location within a macromolecule and electron paramagnetic resonance (EPR) spectroscopy is used to interrogate the local environment surrounding the nitroxide. The SDSL strategy enables probing site-specific structural and dynamic features of RNA in solution without being limited by the size of the molecule, thus serving as a unique tool in biophysical studies of RNA. This chapter describes the use of continuous-wave (cw)-EPR to study dynamic features of RNAs as well as to monitor interactions between them. Various approaches for attaching nitroxide spin labels to nucleic acids are described, followed by detailed descriptions of cw-EPR spectral acquisition and processing procedures. Specific examples are subsequently used to illustrate analysis of EPR spectra, showing how information regarding the parent RNA can be extracted.
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Affiliation(s)
- Xiaojun Zhang
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
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28
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Ward R, Keeble DJ, El-Mkami H, Norman DG. Distance determination in heterogeneous DNA model systems by pulsed EPR. Chembiochem 2008; 8:1957-64. [PMID: 17886320 DOI: 10.1002/cbic.200700245] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Many biological systems, especially those based on nucleic acids, are structurally heterogeneous in solution. We demonstrate here the ability to measure multiple distances, of between 2 and 7 nm, from a heterogeneous mixture of double-spin-labeled DNA duplexes. We have constructed a DNA distance ruler based on the attachment of nitroxide spin labels to 2'-amino-modified nucleosides. The distribution of distances between the spin labels was obtained by Tikhonov regularization analysis of the dipolar coupling evolution data measured by using the electron paramagnetic resonance method, pulsed-electron double resonance (PELDOR). Optimization of the conditions and techniques used in the preparation of the samples has allowed us to increase the sensitivity and reduce aggregation artifacts. As a result, we have been able to demonstrate deconvolution of distances from structurally heterogeneous samples and show the limits of the technique by examining data derived from up to five DNA duplexes, in a single mixture, in which the concentration of each species was as low as 5 microM.
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Affiliation(s)
- Richard Ward
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
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29
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Sowa GZ, Qin PZ. Site-directed spin labeling studies on nucleic acid structure and dynamics. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2008; 82:147-97. [PMID: 18929141 DOI: 10.1016/s0079-6603(08)00005-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Site-directed spin labeling (SDSL) uses electron paramagnetic resonance (EPR) spectroscopy to monitor the behavior of a stable nitroxide radical attached at specific locations within a macromolecule such as protein, DNA, or RNA. Parameters obtained from EPR measurements, such as internitroxide distances and descriptions of the rotational motion of a nitroxide, provide unique information on features near the labeling site. With recent advances in solid-phase synthesis of nucleic acids and developments in EPR methodologies, particularly pulsed EPR technologies, SDSL has been increasingly used to study the structure and dynamics of DNA and RNA at the level of the individual nucleotides. This chapter summarizes the current SDSL studies on nucleic acids, with discussions focusing on literature from the last decade.
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Affiliation(s)
- Glenna Z Sowa
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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30
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Edwards TE, Sigurdsson ST. Site-specific incorporation of nitroxide spin-labels into 2'-positions of nucleic acids. Nat Protoc 2007; 2:1954-62. [PMID: 17703207 DOI: 10.1038/nprot.2007.273] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A protocol is described for the incorporation of nitroxide spin-labels into specific 2'-sites within nucleic acids. This labeling strategy facilitates the investigation of nucleic acid structure and dynamics using electron paramagnetic resonance (EPR) spectroscopy and macromolecular complex formation using paramagnetic relaxation enhancement NMR spectroscopy. A spin-labeling reagent, 4-isocyanato TEMPO, which can be prepared in one facile step or obtained commercially, is used for postsynthetic modification of site-specifically 2'-amino-modified nucleic acids. This spin-labeling protocol has been applied primarily to RNA, but is also applicable to DNA. Subsequently, EPR spectroscopic analysis of the spin-labeled nucleic acids allows for the measurements of distances, solvent accessibilities and conformation dynamics. Using the spin-labeling strategy described here, spin-labeled samples can be prepared in 2-4 d.
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Affiliation(s)
- Thomas E Edwards
- University of Iceland, Science Institute, Dunhaga 3, Reykjavik, Iceland
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31
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Barhate N, Cekan P, Massey AP, Sigurdsson ST. A nucleoside that contains a rigid nitroxide spin label: a fluorophore in disguise. Angew Chem Int Ed Engl 2007; 46:2655-8. [PMID: 17309085 DOI: 10.1002/anie.200603993] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Nivrutti Barhate
- Department of Chemistry, University of Washington, Seattle, WA 98195-1700, USA
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32
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Casiano-Negroni A, Sun X, Al-Hashimi HM. Probing Na(+)-induced changes in the HIV-1 TAR conformational dynamics using NMR residual dipolar couplings: new insights into the role of counterions and electrostatic interactions in adaptive recognition. Biochemistry 2007; 46:6525-35. [PMID: 17488097 PMCID: PMC3319146 DOI: 10.1021/bi700335n] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Many regulatory RNAs undergo large changes in structure upon recognition of proteins and ligands, but the mechanism by which this occurs remains poorly understood. Using NMR residual dipolar coupling (RDCs), we characterized Na+-induced changes in the structure and dynamics of the bulge-containing HIV-1 transactivation response element (TAR) RNA that mirrors changes induced by small molecules bearing a different number of cationic groups. Increasing the Na+ concentration from 25 to 320 mM led to a continuous reduction in the average inter-helical bend angle (from 46 degrees to 22 degrees ), inter-helical twist angle (from 66 degrees to -18 degrees ), and inter-helix flexibility (as measured by an increase in the internal generalized degree of order from 0.56 to 0.74). Similar conformational changes were observed with Mg2+, indicating that nonspecific electrostatic interactions drive the conformational transition, although results also suggest that Na+ and Mg2+ may associate with TAR in distinct modes. The transition can be rationalized on the basis of a population-weighted average of two ensembles comprising an electrostatically relaxed bent and flexible TAR conformation that is weakly associated with counterions and a globally rigid coaxial conformation that has stronger electrostatic potential and association with counterions. The TAR inter-helical orientations that are stabilized by small molecules fall around the metal-induced conformational pathway, indicating that counterions may help predispose the TAR conformation for target recognition. Our results underscore the intricate sensitivity of RNA conformational dynamics to environmental conditions and demonstrate the ability to detect subtle conformational changes using NMR RDCs.
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Affiliation(s)
| | | | - Hashim M. Al-Hashimi
- To whom correspondence should be addressed. H. M. A.: ; telephone (734) 615 3361; fax (734) 647 4865
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33
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Barhate N, Cekan P, Massey A, Sigurdsson S. A Nucleoside That Contains a Rigid Nitroxide Spin Label: A Fluorophore in Disguise. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200603993] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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34
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Nakano SI, Kirihata T, Fujii S, Sakai H, Kuwahara M, Sawai H, Sugimoto N. Influence of cationic molecules on the hairpin to duplex equilibria of self-complementary DNA and RNA oligonucleotides. Nucleic Acids Res 2006; 35:486-94. [PMID: 17169988 PMCID: PMC1802612 DOI: 10.1093/nar/gkl1073] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
A self-complementary nucleotide sequence can form both a unimolecular hairpin and a bimolecular duplex. In this study, the secondary structures of the self-complementary DNA and RNA oligonucleotides with different sequences and lengths were investigated under various solution conditions by gel electrophoresis, circular dichroism (CD) and electron paramagnetic resonance (EPR) spectroscopy and a ultraviolet (UV) melting analysis. The DNA sequences tended to adopt a hairpin conformation at low cation concentrations, but a bimolecular duplex was preferentially formed at an elevated cationic strength. On the other hand, fully matched RNA sequences adopted a bimolecular duplex regardless of the cation concentration. The thermal melting experiments indicated a greater change in the melting temperature of the bimolecular duplexes (by approximately 20 degrees C) than that of the hairpin (by approximately 10 degrees C) by increasing the NaCl concentration from 10 mM to 1 M. Hairpin formations were also observed for the palindrome DNA sequences derived from Escherichia coli, but association of the complementary palindrome sequences was observed when spermine, one of the major cationic molecules in a cell, existed at the physiological concentration. The results indicate the role of cations for shifting the structural equilibrium toward a nucleotide assembly and implicate nucleotide structures in cells.
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Affiliation(s)
- Shu-ichi Nakano
- Frontier Institute for Biomolecular Engineering Research (FIBER)8–9–1 Okamoto, Higashinada–ku, Kobe 658–8501, Japan
| | - Toshimasa Kirihata
- Department of Chemistry, Faculty of Science and Engineering, Konan University8–9–1 Okamoto, Higashinada–ku, Kobe 658–8501, Japan
| | - Satoshi Fujii
- Frontier Institute for Biomolecular Engineering Research (FIBER)8–9–1 Okamoto, Higashinada–ku, Kobe 658–8501, Japan
- Department of Chemistry, Faculty of Science and Engineering, Konan University8–9–1 Okamoto, Higashinada–ku, Kobe 658–8501, Japan
| | - Hiroshi Sakai
- Department of Chemistry, Faculty of Science and Engineering, Konan University8–9–1 Okamoto, Higashinada–ku, Kobe 658–8501, Japan
| | - Masayasu Kuwahara
- Faculty of Engineering, Gunma University1-5-1 Tenjin-chou, Kiryu, Gunma 376-8515, Japan
- PRESTO, Japan Science and Technology Agency (JST)Saitama 332-0012, Japan
| | - Hiroaki Sawai
- Faculty of Engineering, Gunma University1-5-1 Tenjin-chou, Kiryu, Gunma 376-8515, Japan
| | - Naoki Sugimoto
- Frontier Institute for Biomolecular Engineering Research (FIBER)8–9–1 Okamoto, Higashinada–ku, Kobe 658–8501, Japan
- Department of Chemistry, Faculty of Science and Engineering, Konan University8–9–1 Okamoto, Higashinada–ku, Kobe 658–8501, Japan
- To whom correspondence should be addressed. Tel: +81 78 435 2497; Fax: +81 78 435 2539;
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35
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Kang G, Lin X. RNA Modified Electrodes for Simultaneous Determination of Dopamine and Uric Acid in the Presence of High Amounts of Ascorbic Acid. ELECTROANAL 2006. [DOI: 10.1002/elan.200603701] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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36
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Cai Q, Kusnetzow AK, Hubbell WL, Haworth IS, Gacho GPC, Van Eps N, Hideg K, Chambers EJ, Qin PZ. Site-directed spin labeling measurements of nanometer distances in nucleic acids using a sequence-independent nitroxide probe. Nucleic Acids Res 2006; 34:4722-30. [PMID: 16966338 PMCID: PMC1635252 DOI: 10.1093/nar/gkl546] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Revised: 06/30/2006] [Accepted: 07/13/2006] [Indexed: 11/12/2022] Open
Abstract
In site-directed spin labeling (SDSL), local structural and dynamic information is obtained via electron paramagnetic resonance (EPR) spectroscopy of a stable nitroxide radical attached site-specifically to a macromolecule. Analysis of electron spin dipolar interactions between pairs of nitroxides yields the inter-nitroxide distance, which provides quantitative structural information. The development of pulse EPR methods has enabled such distance measurements up to 70 A in bio-molecules, thus opening up the possibility of SDSL global structural mapping. This study evaluates SDSL distance measurement using a nitroxide (designated as R5) that can be attached, in an efficient and cost-effective manner, to a phosphorothioate backbone position at arbitrary DNA or RNA sequences. R5 pairs were attached to selected positions of a dodecamer DNA duplex with a known NMR structure, and eight distances, ranging from 20 to 40 A, were measured using double electron-electron resonance (DEER). The measured distances correlated strongly (R2 = 0.98) with the predicted values calculated based on a search of sterically allowable R5 conformations in the NMR structure, thus demonstrating accurate distance measurements using R5. Furthermore, distance measurement in a 42 kD DNA was demonstrated. The results establish R5 as a sequence-independent probe for global structural mapping of DNA and DNA-protein complexes.
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Affiliation(s)
- Qi Cai
- Department of Chemistry , University of Southern CaliforniaLos Angeles, CA 90089-0744, USA
| | - Ana Karin Kusnetzow
- Jules Stein Eye Institute and Department of Chemistry and Biochemistry, University of CaliforniaLos Angeles, CA 90095, USA
| | - Wayne L. Hubbell
- Jules Stein Eye Institute and Department of Chemistry and Biochemistry, University of CaliforniaLos Angeles, CA 90095, USA
| | - Ian S. Haworth
- Department of Pharmaceutical Sciences, University of Southern CaliforniaLos Angeles, CA 90089, USA
| | - Gian Paola C. Gacho
- Department of Chemistry , University of Southern CaliforniaLos Angeles, CA 90089-0744, USA
| | - Ned Van Eps
- Jules Stein Eye Institute and Department of Chemistry and Biochemistry, University of CaliforniaLos Angeles, CA 90095, USA
| | - Kálmán Hideg
- Institute of Organic and Medical Chemistry, University of PécsH-7643, Pécs, P.O. Box 99, Hungary
| | - Eric J. Chambers
- Department of Pharmaceutical Sciences, University of Southern CaliforniaLos Angeles, CA 90089, USA
| | - Peter Z. Qin
- Department of Chemistry , University of Southern CaliforniaLos Angeles, CA 90089-0744, USA
- Department of Biological Sciences, University of Southern CaliforniaLos Angeles, CA 90089-0744, USA
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37
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Edwards TE, Sigurdsson ST. EPR Spectroscopic Analysis of U7 Hammerhead Ribozyme Dynamics during Metal Ion Induced Folding. Biochemistry 2005; 44:12870-8. [PMID: 16171402 DOI: 10.1021/bi050549g] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy was used to examine changes in internal structure and dynamics of the hammerhead ribozyme upon metal ion induced folding, changes in pH, and the presence and absence of ribozyme inhibitors. A nitroxide spin-label was attached to nucleotide U7 of the HH16 catalytic core, and this modified ribozyme was observed to retain catalytic activity. U7 was shown by EPR spectroscopy to be more mobile in the ribozyme-product complex than in either the unfolded ribozyme or the ribozyme-substrate complex. A two-step divalent metal ion dependent folding pathway was observed for the ribozyme-substrate complex with a weak first transition observed at 0.25 mM Mg2+ and a strong second transition observed around 10 mM Mg2+, in agreement with studies using other biophysical and biochemical techniques. Previously, ribozyme activity was observed in the absence of divalent metal ions and the presence of high concentrations of monovalent metal ions, although the activity was less than that observed in the presence of divalent metal ions. Here, we observed similar dynamics for U7 in the presence of 4 M Na+ or Li+, which were distinctively different than that observed in the presence of 10 mM Mg2+, indicating that U7 of the catalytic core forms a different microenvironment under monovalent versus divalent metal ion conditions. Interestingly, the catalytically efficient microenvironment of U7 was similar to that observed in a solution containing 1 M Na+ upon addition of one divalent metal ion per ribozyme. In summary, these results demonstrate that changes in local dynamics, as detected by EPR spectroscopy, can be used to study conformational changes associated with RNA folding and function.
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Affiliation(s)
- Thomas E Edwards
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
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Qin PZ, Feigon J, Hubbell WL. Site-directed spin labeling studies reveal solution conformational changes in a GAAA tetraloop receptor upon Mg(2+)-dependent docking of a GAAA tetraloop. J Mol Biol 2005; 351:1-8. [PMID: 15993422 DOI: 10.1016/j.jmb.2005.06.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Revised: 05/31/2005] [Accepted: 06/01/2005] [Indexed: 11/23/2022]
Abstract
The Mg(2+)-dependent GAAA tetraloop interaction with its 11 nucleotide receptor is one of the most frequently occurring long-range tertiary interactions in RNAs. To explore conformational changes in the receptor during tetraloop docking, nitroxide spin labels were attached at each of four uridine bases, one at a time, within an RNA molecule containing the receptor sequence. In the presence of Mg2+ and the tetraloop, the electron paramagnetic resonance (EPR) spectrum of one of the labeled bases reflected a large increase in mobility, indicating unstacking of the base upon tetraloop docking. This provides direct evidence that base unstacking is an intrinsic feature of the solution tetraloop-receptor complex formed in the presence of Mg2+. Additional evidence suggests that in solution the bound receptor conformation is similar to that observed in the crystal structure of a group I intron ribozyme domain. In Mg2+ alone, a receptor conformation with an unstacked base was not detectable, suggesting that this conformation is of higher standard state free energy than that of the free receptor. This leads to the conclusion that the extensive RNA-RNA interactions observed in the crystal structure of the tetraloop-receptor complex provide larger interaction energy than the measured apparent affinity between the tetraloop and the free receptor. This is compatible with a high specificity of the tetraloop-receptor interaction.
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Affiliation(s)
- Peter Z Qin
- Jules Stein Eye Institute, University of California, Los Angeles, CA 90095, USA.
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39
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Edwards TE, Robinson BH, Sigurdsson ST. Identification of amino acids that promote specific and rigid TAR RNA-tat protein complex formation. ACTA ACUST UNITED AC 2005; 12:329-37. [PMID: 15797217 DOI: 10.1016/j.chembiol.2005.01.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2004] [Revised: 01/19/2005] [Accepted: 01/20/2005] [Indexed: 11/28/2022]
Abstract
The Tat protein and the transactivation responsive (TAR) RNA form an essential complex in the HIV lifecycle, and mutations in the basic region of the Tat protein alter this RNA-protein molecular recognition. Here, EPR spectroscopy was used to identify amino acids, flanking an essential arginine of the Tat protein, which contribute to specific and rigid TAR-Tat complex formation by monitoring changes in the mobility of nitroxide spin-labeled TAR RNA nucleotides upon binding. Arginine to lysine N-terminal mutations did not affect TAR RNA interfacial dynamics. In contrast, C-terminal point mutations, R56 in particular, affected the mobility of nucleotides U23 and U38, which are involved in a base-triple interaction in the complex. This report highlights the role of dynamics in specific molecular complex formation and demonstrates the ability of EPR spectroscopy to study interfacial dynamics of macromolecular complexes.
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Affiliation(s)
- Thomas E Edwards
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
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Hollman AM, Christian DA, Ray PD, Galey D, Turchan J, Nath A, Bhattacharyya D. Selective isolation and purification of tat protein via affinity membrane separation. Biotechnol Prog 2005; 21:451-9. [PMID: 15801785 DOI: 10.1021/bp049804z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This work deals with the separation of Tat protein from a complex fermentation broth using an affinity membrane system. Tat is a regulatory protein that is critical for HIV-1 replication and thus a potential candidate for vaccine and drug development. Furthermore, Tat can facilitate transport of exogenous molecules across cell membranes and is implicated in pathogenesis of HIV dementia. Affinity membranes were prepared through coupling of avidin within a 4-stack membrane construct. Tat (naturally biotinylated) accessibility in the bacterial lysate feed was influenced by the presence of RNAse, protein concentration, and ionic strength. Enhanced accessibility translated to a marked increase in the overall product yield per pass. The purity of the membrane-isolated Tat was compared to that prepared via packed column chromatography through SDS-PAGE, Western blot, activity assay, and neurotoxicity studies. Tat protein produced via membrane separation yielded primarily monomeric forms of the oligopeptide sequence, whereas column chromatography produced predominately polymeric forms of Tat. These differences resulted in changes in the neurotoxicity and cellular uptake of the two preparations.
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Affiliation(s)
- Aaron M Hollman
- Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506-0046, USA
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Olsen GL, Edwards TE, Deka P, Varani G, Sigurdsson ST, Drobny GP. Monitoring tat peptide binding to TAR RNA by solid-state 31P-19F REDOR NMR. Nucleic Acids Res 2005; 33:3447-54. [PMID: 15961729 PMCID: PMC1151589 DOI: 10.1093/nar/gki626] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Revised: 05/13/2005] [Accepted: 05/13/2005] [Indexed: 11/17/2022] Open
Abstract
Complexes of the HIV transactivation response element (TAR) RNA with the viral regulatory protein tat are of special interest due in particular to the plasticity of the RNA at this binding site and to the potential for therapeutic targeting of the interaction. We performed REDOR solid-state NMR experiments on lyophilized samples of a 29 nt HIV-1 TAR construct to measure conformational changes in the tat-binding site concomitant with binding of a short peptide comprising the residues of the tat basic binding domain. Peptide binding was observed to produce a nearly 4 A decrease in the separation between phosphorothioate and 2'F labels incorporated at A27 in the upper helix and U23 in the bulge, respectively, consistent with distance changes observed in previous solution NMR studies, and with models showing significant rearrangement in position of bulge residue U23 in the bound-form RNA. In addition to providing long-range constraints on free TAR and the TAR-tat complex, these results suggest that in RNAs known to undergo large deformations upon ligand binding, 31P-19F REDOR measurements can also serve as an assay for complex formation in solid-state samples. To our knowledge, these experiments provide the first example of a solid-state NMR distance measurement in an RNA-peptide complex.
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Affiliation(s)
- Greg L. Olsen
- Department of Chemistry, University of WashingtonSeattle, WA 98195-1700, USA
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center1100 Fairview Avenue North, Seattle, WA 98109, USA
- Science Institute, University of IcelandDunhaga 3, IS-107 Reykjavik, Iceland
| | - Thomas E. Edwards
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center1100 Fairview Avenue North, Seattle, WA 98109, USA
| | - Pritilekha Deka
- Department of Chemistry, University of WashingtonSeattle, WA 98195-1700, USA
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center1100 Fairview Avenue North, Seattle, WA 98109, USA
- Science Institute, University of IcelandDunhaga 3, IS-107 Reykjavik, Iceland
| | - Gabriele Varani
- Department of Chemistry, University of WashingtonSeattle, WA 98195-1700, USA
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center1100 Fairview Avenue North, Seattle, WA 98109, USA
- Science Institute, University of IcelandDunhaga 3, IS-107 Reykjavik, Iceland
| | | | - Gary P. Drobny
- To whom correspondence should be addressed. Tel: +1 206 685 2052; Fax: +1 206 685 8665;
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Darian E, Gannett PM. Application of molecular dynamics simulations to spin-labeled oligonucleotides. J Biomol Struct Dyn 2005; 22:579-93. [PMID: 15702930 DOI: 10.1080/07391102.2005.10507028] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The EPR study of spin labeled macromolecules has provided insight into structural and dynamical properties of DNA, proteins, and related systems. While spin labeling has been useful, it is experimentally difficult to determine if the spin label significantly alters the conformation of the macromolecule to which it is attached. Molecular modeling has proven to be a powerful tool for studying structure and dynamics of biologically important molecules. Here, we have conducted molecular dynamics (MD) studies of spin labeled oligonucleotides (ONs) bearing a five (5sp) or six (6sp) membered ring nitroxide, and the corresponding unmodified ON using the suite of programs contained in Amber 5.0 with the Cornell et al. 94 force field (Cornell, W. D., Cieplak, P., Bayly, C. I., Gould, I. R., Merz, Jr., K. M. Ferguson, D. M., Spellmeyer, D. C., Fox, T., Caldwell, J. W., and Kollman, P. A. A Second Generation Force Field for the Simulation of Proteins and Nucleic Acids. J. Am. Chem. Soc. 117, 5179-5197 (1995)). Quantum mechanical calculations employing the B3LYP method with the standard 6-31G* basis set using Gaussian98 were performed and, together with available crystallographic data for analogous nitroxides, new parameters for the nitrogen, oxygen, nitroxide alpha-carbon, and sp-hybridized carbon atoms have been developed suitable for the Cornell et al. 94 force field. MD simulations on the double-stranded (ds) spin labeled ONs, along with the corresponding unmodified analogues, have been studied over the course of 4 ns and conformational properties of all ONs are described based on the analysis of the trajectories. The spin labels were found to alter the global conformation of the ONs to which they were attached to accommodate the spin labels. The major changes include widening the major groove, decreasing helical twist, and more negative X-displacement of the base pairs. The magnitude of the effect was dependent on the specific structure of the spin label. Average and 'most representative' structures derived from the molecular dynamics simulations correlate with the experimental data on the spin labeled ONs.
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Affiliation(s)
- Eva Darian
- Dept. of Basic Pharmaceutical Sciences, West Virginia University, P.O. Box 9530, Morgantown, WV 26506, USA
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Kim NK, Murali A, DeRose VJ. A distance ruler for RNA using EPR and site-directed spin labeling. ACTA ACUST UNITED AC 2005; 11:939-48. [PMID: 15271352 DOI: 10.1016/j.chembiol.2004.04.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2003] [Revised: 03/29/2004] [Accepted: 04/21/2004] [Indexed: 10/26/2022]
Abstract
As a basic model study for measuring distances in RNA molecules using continuous wave (CW) EPR spectroscopy, site-directed spin-labeled 10-mer RNA duplexes and HIV-1 TAR RNA motifs with various interspin distances were examined. The spin labels were attached to the 2'-NH2 positions of appropriately placed uridines in the duplexes, and interspin distances were measured from both molecular dynamics simulations (MD) and Fourier deconvolution methods (FD). The 10-mer duplexes have interspin distances ranging from 10 A to 30 A based on MD; however, dipolar line broadening of the CW EPR spectrum is only observed for the RNAs for predicted interspin distances of 10-21 A and not for distances over 25 A. The conformational changes in TAR (transactivating responsive region) RNA in the presence and in the absence of different divalent metal ions were monitored by measuring distances between two nucleotides in the bulge region. The predicted interspin distances obtained from the FD method and those from MD calculations match well for both the model RNA duplexes and the structural changes predicted for TAR RNA. These results demonstrate that distance measurement using EPR spectroscopy is a potentially powerful method to help predict the structures of RNA molecules.
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Affiliation(s)
- Nak-Kyoon Kim
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, USA
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44
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Abstract
The application of techniques based on magnetic resonance, specifically electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR), has provided a wealth of new information on RNA structures, as well as insights into the dynamics and function of these important biomolecules. NMR spectroscopy is very successful for determining the solution structures of small RNA domains, aptamers and ribozymes, and exploring their intramolecular dynamics and interactions with ligands. EPR-based methods have been used to map local dynamic and structural features of RNA, to explore different modes of RNA-ligand interaction, to obtain long-range structural restraints and to probe metal-ion-binding sites.
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Affiliation(s)
- Peter Z Qin
- Department of Chemistry, University of Southern California, LJS-251, 840 Downey Way, Los Angeles, California 90089-0744, USA.
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Minunni M, Tombelli S, Gullotto A, Luzi E, Mascini M. Development of biosensors with aptamers as bio-recognition element: the case of HIV-1 Tat protein. Biosens Bioelectron 2004; 20:1149-56. [PMID: 15556361 DOI: 10.1016/j.bios.2004.03.037] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Revised: 03/02/2004] [Accepted: 03/04/2004] [Indexed: 10/26/2022]
Abstract
The in vitro selection of combinatorial libraries of RNA/DNA, has allowed the identification of specific nucleic acids (aptamers) which bind to a wide range of target molecules with high affinity and specificity. In this work, an RNA aptamer, specific for the protein trans-activator of transcription (Tat) of HIV-1, has been used as bio-recognition element to develop a biosensor (aptasensor). The biosensor was optimised using piezoelectric quartz-crystals as transducers and the aptamer was immobilised on the gold electrode of the crystal. The immobilisation procedure was based on the interaction between the biotinylated aptamer and streptavidin previously deposited on the electrode. The main analytical characteristics of the biosensor, such as sensitivity, selectivity and reproducibility, have been studied in details. An optimised regeneration procedure allowed the multiple use of the aptamer-coated crystal. The aptasensor has been compared with the corresponding immunosensor, based on the specific monoclonal anti-Tat antibody. The antibody was immobilised on a layer of carboxylated dextran previously deposited on the gold electrode. The results demonstrated that the use of a biosensor with a specific aptamer as bio-recognition element could be an interesting approach in the detection of proteins, which has been here examined considering a model system.
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Affiliation(s)
- M Minunni
- Università degli Studi di Firenze, Dipartimento di Chimica, Via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy
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Schiemann O, Piton N, Mu Y, Stock G, Engels JW, Prisner TF. A PELDOR-based nanometer distance ruler for oligonucleotides. J Am Chem Soc 2004; 126:5722-9. [PMID: 15125665 DOI: 10.1021/ja0393877] [Citation(s) in RCA: 164] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A pulsed electron paramagnetic resonance (EPR) spectroscopic ruler for oligonucleotides was developed using a series of duplex DNAs. The spin-labeling is accomplished during solid-phase synthesis of the oligonucleotides utilizing a palladium-catalyzed cross-coupling reaction between 5-iodo-2'-deoxyuridine and the rigid spin-label 2,2,5,5-tetramethyl-pyrrolin-1-yloxyl-3-acetylene (TPA). 4-Pulse electron double resonance (PELDOR) was then used to measure the intramolecular spin-spin distances via the dipolar coupling, yielding spin-spin distances of 19.2, 23.3, 34.7, 44.8, and 52.5 A. Employing a full-atom force field with explicit water, molecular dynamic (MD) simulations on the same spin-labeled oligonucleotides in their duplex B-form gave spin-spin distances of 19.6, 21.4, 33.0, 43.3, and 52.5 A, respectively, in very good agreement with the measured distances. This shows that the oligonucleotides adopt a B-form duplex structure also in frozen aqueous buffer solution. It also demonstrates that the combined use of site-directed spin-labeling, PELDOR experiments, and MD simulations can yield a microscopic picture about the overall structure of oligonucleotides. The technique is also applicable to more complex systems, like ribozymes or DNA/RNA-protein complexes, which are difficult to access by NMR or X-ray crystallography.
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Affiliation(s)
- Olav Schiemann
- Institute of Physical and Theoretical Chemistry, Marie-Curie-Strasse 11, J. W. Goethe-University, Frankfurt am Main, Germany.
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48
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Pitt SW, Majumdar A, Serganov A, Patel DJ, Al-Hashimi HM. Argininamide binding arrests global motions in HIV-1 TAR RNA: comparison with Mg2+-induced conformational stabilization. J Mol Biol 2004; 338:7-16. [PMID: 15050819 PMCID: PMC4694592 DOI: 10.1016/j.jmb.2004.02.031] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2003] [Revised: 02/04/2004] [Accepted: 02/11/2004] [Indexed: 10/26/2022]
Abstract
The structure and dynamics of the stem-loop transactivation response element (TAR) RNA from the human immunodeficiency virus type-1 (HIV-1) bound to the ligand argininamide (ARG) has been characterized using a combination of a large number of residual dipolar couplings (RDCs) and trans-hydrogen bond NMR methodology. Binding of ARG to TAR changes the average inter-helical angle between the two stems from approximately 47 degrees in the free state to approximately 11 degrees in the bound state, and leads to the arrest of large amplitude (+/-46 degrees ) inter-helical motions observed previously in the free state. While the global structural dynamics of TAR-ARG is similar to that previously reported for TAR bound to Mg2+, there are substantial differences in the hydrogen bond alignment of bulge and neighboring residues. Based on a novel H5(C5)NN experiment for probing hydrogen-mediated 2hJ(N,N) scalar couplings as well as measured RDCs, the TAR-ARG complex is stabilized by a U38-A27.U23 base-triple involving an A27.U23 reverse Hoogsteen hydrogen bond alignment as well as by a A22-U40 Watson-Crick base-pair at the junction of stem I. These hydrogen bond alignments are not observed in either the free or Mg2+ bound forms of TAR. The combined conformational analysis of TAR under three states reveals that ligands and divalent ions can stabilize similar RNA global conformations through distinct interactions involving different hydrogen bond alignments in the RNA.
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Affiliation(s)
- Stephen W. Pitt
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Ananya Majumdar
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
| | - Alexander Serganov
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
| | - Dinshaw J. Patel
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
| | - Hashim M. Al-Hashimi
- Departments of Chemistry and Biophysics Research Division, University of Michigan, Ann Arbor, MI 48109, USA
- Corresponding author:
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49
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Schiemann O, Fritscher J, Kisseleva N, Sigurdsson ST, Prisner TF. Structural Investigation of a High-Affinity MnII Binding Site in the Hammerhead Ribozyme by EPR Spectroscopy and DFT Calculations. Effects of Neomycin B on Metal-Ion Binding. Chembiochem 2003; 4:1057-65. [PMID: 14523924 DOI: 10.1002/cbic.200300653] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electron paramagnetic resonance spectroscopy and density functional theory methods were used to study the structure of a single, high-affinity Mn(II) binding site in the hammerhead ribozyme. This binding site exhibits a dissociation constant Ke of 4.4 microM in buffer solutions containing 1 M NaCl, as shown by titrations monitored by continuous wave (cw) EPR. A combination of electron spin echo envelope modulation (ESEEM) and hyperfine sublevel correlation (HYSCORE) experiments revealed that the paramagnetic manganese(II) ion in this binding site is coupled to a single nitrogen atom with a quadrupole coupling constant kappa of 0.7 MHz, an asymmetry parameter eta of 0.4, and an isotropic hyperfine coupling constant of Aiso(14N)=2.3 MHz. All three EPR parameters are sensitive to the arrangement of the Mn(II) ligand sphere and can therefore be used to determine the structure of the binding site. A possible location for this binding site may be at the G10.1, A9 site found to be occupied by Mn(II) in crystals (MacKay et al., Nature 1994, 372, 68 and Scott et al., Science 1996, 274, 2065). To determine whether the structure of the binding site is the same in frozen solution, we performed DFT calculations for the EPR parameters, based on the structure of the Mn(II) site in the crystal. Computations with the BHPW91 density function in combination with a 9s7p4d basis set for the manganese(II) center and the Iglo-II basis set for all other atoms yielded values of kappa(14N)=+0.80 MHz, eta=0.324, and Aiso(14N)=+2.7 MHz, in excellent agreement with the experimentally obtained EPR parameters, which suggests that the binding site found in the crystal and in frozen solution are the same. In addition, we demonstrated by EPR that Mn(II) is released from this site upon binding of the aminoglycoside antibiotic neomycin B (Kd=1.2 microM) to the hammerhead ribozyme. Neomycin B has previously been shown to inhibit the catalytic activity of this ribozyme (Uhlenbeck et al., Biochemistry 1995, 34, 11 186).
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Affiliation(s)
- Olav Schiemann
- Department of Physical and Theoretical Chemistry, and Center for Biological Magnetic Resonance, Johann Wolfgang Goethe University, Marie-Curie-Strasse 11, 60439 Frankfurt/Main, Germany.
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50
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Abstract
Metal ion-induced changes in HIV-1 TAR RNA internal dynamics were determined by the changes in EPR spectral width for TAR RNAs containing spin-labeled nucleotides (U23, U25, U38, and U40). This gave a dynamic signature for each of 10 metal ions studied, which fell into one of three distinct groups. While Li(+) and K(+) had little effect on TAR RNA internal dynamics, Na(+) unexpectedly had a dynamic signature that was similar to Ca(2+) and Sr(2+), with a decrease in mobility at U23 and U38, little or no change at U25, and an increase in mobility at U40. Mg(2+), Co(2+), Ni(2+), Zn(2+), and Ba(2+) had similar effects on U23, U38, and U40, but the mobility of U25 was markedly increased. Our results show that RNA dynamics change upon metal binding to the TAR RNA bulge, indicating that RNA structure adapts to accommodate metal ions of different size and coordination properties.
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Affiliation(s)
- Thomas E Edwards
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700, USA
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